R help - Feb 2009 - Suggestions on which package to use

Hi all,

I have been working with the chron package thanks to some guidance 
from Gabor Grothendieck so I could plot activity by times.

What it the best or "recommended" package to compare such activity 
between sites?
I want to compare the acetify time (multiple bat species) between 
sites and species to see if there is any significantly difference so 
I can infer some habitat preference or resource availability.

Tnx.